The major objectives of the proposed studies on peptide hormonal control of intestinal ion transport are a better understanding of intestinal transport processes and the determination of the roles of some peptide hormones in regulating these processes. Using electrophysiological and radioactive tracer methodology, the effects of hormonal factors on absorptive and secretory processes will be studied, and, in particular, the effects of naturally-occurring hormone analogs on homologous and heterologous systems. Studies will center on two peptide hormone analog families, somatostatin-urotensin II and corticotropin releasing factor-sauvagine-urotensin I, some members of which have demonstrated effects on either intestial or non-intestinal ion transport. The presence of large numbers of variety of peptide hormone-secreting cells in the intestinal wall suggests the potential importance of these peptides in regulating intestinal function, especially in the various forms of intestinal malabsorption resulting in clinically-important diarrhea and its associated dehydration. Pharmacological agents will be used to assess the roles of intracellular mediators sulch as Ca and cyclic AMP in the observed effects. Together, these biophysical and endocrinological investigations may increase understanding of and appreciation for the role of the intestine in fluid and electrolyte balance.